1. Field of the Invention
The present invention relates generally to methods for fabricating magnetic sensor elements. More particularly, the present invention relates to methods for fabricating magnetoresistive (MR) sensor elements.
2. Description of the Related Art
The recent and continuing advances in computer and information technology have been made possible not only by the correlating advances in the functionality, reliability and speed of semiconductor integrated circuits, but also by the correlating advances in the storage density and reliability of direct access storage devices (DASDs) employed in digitally encoded magnetic data storage and retrieval.
Storage density of direct access storage devices (DASDs) is typically determined as areal storage density of a magnetic data storage medium formed upon a rotating magnetic data storage disk within a direct access storage device (DASD) magnetic data storage enclosure. The areal storage density of the magnetic data storage medium is determined largely by the track width, the track spacing and the linear magnetic domain density within the magnetic data storage medium. The track width, the track spacing and the linear magnetic domain density within the magnetic data storage medium are in turn determined by several principal factors, including but not limited to: (1) the magnetic read-write characteristics of a magnetic read-write head employed in reading and writing digitally encoded magnetic data from and into the magnetic data storage medium; (2) the magnetic domain characteristics of the magnetic data storage medium; and (3) the separation distance of the magnetic read-write head from the magnetic data storage medium.
With regard to the magnetic read-write characteristics of magnetic read-write heads employed in reading and writing digitally encoded magnetic data from and into a magnetic data storage medium, it is known in the art of magnetic read-write head fabrication that magnetoresistive (MR) sensor elements employed within magnetoresistive (MR) read-write heads are generally superior to other types of magnetic sensor elements when employed in retrieving digitally encoded magnetic data from a magnetic data storage medium. In that regard, magnetoresistive (MR) sensor elements are generally regarded as superior since magnetoresistive (MR) sensor elements are known in the art to provide high output digital read signal amplitudes, with good linear resolution, independent of the relative velocity of a magnetic data storage medium with respect to a magnetoresistive (MR) read-write head having the magnetoresistive (MR) sensor element incorporated therein.
While magnetoresistive (MR) sensor elements are thus desirable within the art of digitally encoded magnetic data storage and retrieval, magnetoresistive (MR) sensor elements are nonetheless not entirely without problems within the art of digitally encoded magnetic data storage and retrieval. In particular, as patterned magnetoresistive (MR) layers within magnetoresistive (MR) sensor elements become smaller in dimension, it becomes increasingly more important and more difficult to reliably form those patterned magnetoresistive (MR) layers with a precise and limited stripe height while employing lapping methods as are conventional in the art of magnetoresistive (MR) sensor element fabrication.
It is thus towards the goal of providing, for use when fabricating magnetoresistive (MR) sensor elements, methods for reliably forming patterned magnetoresistive (MR) layers with precise and limited stripe height that the present invention is directed.
Various methods and resultant magnetoresistive (MR) sensor element structures have been disclosed in the art of magnetoresistive (MR) sensor element fabrication for forming patterned magnetoresistive (MR) layers with desirable properties.
For example, Zammit, in U.S. Pat. No. 5,065,483 and U.S. Pat. No. 5,210,667 discloses a method, and a magnetoresistive (MR) sensor element fabricated in accord with the method, where the magnetoresistive (MR) sensor element has formed therein a patterned magnetoresistive (MR) layer with precise stripe height. To achieve that result, the method employs a magnetoresistive (MR) lapping monitor employing a lapped resistive layer and an unlapped standard resistive layer such that measurement of a difference in resistance between the lapped resistive layer and the untapped standard resistive layer provides for control of a lapping method which simultaneously provides within the magnetoresistive (MR) sensor element the patterned magnetoresistive (MR) layer with the precise stripe height.
In addition, Mowry et al., in U.S. Pat. No. 5,559,429 analogously also discloses a system for lapping within a magnetoresistive (MR) sensor element a patterned magnetoresistive (MR) layer to a precise stripe height. The method employs a magnetoresistive (MR) lapping monitor comprising a lapped resistive layer, an untapped target resistive layer and an untapped reference resistive layer, such that measurement of differences in resistance between the lapped resistive layer in conjunction with the untapped target resistive layer and the untapped reference resistive layer provides for control of a lapping method which simultaneously provides within the magnetoresistive (MR) sensor element the patterned magnetoresistive (MR) layer with the precise stripe height.
Further, although not specifically directed to a magnetoresistive (MR) lapping monitor or a lapping method for forming a patterned magnetoresistive (MR) layer with a precise stripe height within a magnetoresistive (MR) sensor element, Mallary, in U.S. Pat. No. 5,654,854, discloses a magnetoresistive (MR) sensor element wherein a central portion of an edge of a patterned magnetoresistive (MR) layer opposite an air bearing surface edge of the patterned magnetoresistive (MR) layer is formed with a concavity. The patterned magnetoresistive (MR) layer so formed with the concave edge opposite the air bearing surface edge of the patterned magnetoresistive (MR) layer exhibits a single domain structure within the patterned magnetoresistive (MR) layer and thus provides attenuated Barkhausen noise within a magnetoresistive (MR) sensor element fabricated employing the patterned magnetoresistive (MR) layer.
Yet further, Shibata et al., in U.S. Pat. No. 5,708,370, discloses yet another magnetoresistive lapping monitor for forming within a magnetoresistive (MR) sensor element a patterned magnetoresistive (MR) layer with precise stripe height. The magnetoresistive (MR) lapping monitor employs both a continuously variable resistance lapped resistive layer and a discontinuously variable resistance lapped resistive layer, both of which are lapped simultaneously with the patterned magnetoresistive (MR) layer within the magnetoresistive (MR) sensor element.
Finally, Rottmayer et al., in U.S. Pat. No. 5,772,493, discloses a lapping control apparatus and a method for using the lapping control apparatus to control an offset of a patterned magnetoresistive (MR) layer with respect to a pair of magnetic shield layers which shield the patterned magnetoresistive (MR) layer within a magnetoresistive (MR) sensor element. The apparatus and method employ a magnetic excitation field which induces a variable current within the patterned magnetoresistive (MR) layer as a function of an offset distance of the patterned magnetoresistive (MR) layer with respect to the pair of magnetic shield layers when the pair of magnetic shield layers is lapped when forming the magnetoresistive (MR) sensor element.
Desirable in the art of magnetoresistive (MR) sensor element fabrication are additional methods which may be employed to form within magnetoresistive (MR) sensor element fabrications patterned magnetoresistive (MR) layers with precise stripe heights.
It is towards that goal that the present invention is directed.